Fatigue and sleep problems such as insomnia or hypersomnia are common after a brain injury. However, they are complicated problems that may have multiple sources. A recent research review outline the possible ways that a brain injury can cause fatigue or sleep problems.
There are different types of fatigue that can occur after a brain injury:
Primary fatigue-occurs as a result of disease or disorder. A diffuse axonal injury or injury to the pituitary gland are two ways in which a brain injury can cause primary fatigue.
Secondary fatigue-occurs as an exacerbation of primary fatigue when resources are low, such as when there are sleep problems, depression, anxiety, or pain.
Psychological fatigue-is "a state of weariness" due to chronic stress, increased mental effort, or psychological distress, which are common after a brain injury.
Sleep problems may result from different sources:
Physical changes-damage to certain areas of the brain such as the reticular activating system or the limbic system can result in hypersomnia (excessive sleepiness). Damage to areas such as the frontal lobe may result in anxiety and depression, which may lead to insomnia.
Hormonal changes-damage to the hypothalamus or pituitary gland may disrupt the sleep-wake cycle. In particular, melatonin, a hormone related to the sleep-wake cycle, has been shown to be significantly lower in people who have a brain injury.
Ponsford JL, Ziino C, Parcell DL, et al. Fatigue and sleep disturbance following traumatic brain injury-Their nature, causes, and potential treatments. Journal of Head Trauma Rehabilitation. (June 2012).